1. Field of the Invention
The present invention relates to a line interpolation apparatus, and relates in particular to a line interpolation apparatus that converts an interlaced video scan signal, such as an NTSC television signal or a PAL television signal, into a progressive video scan signal.
The present invention also relates to a video signal conversion device for performing a video signal conversion to obtain a video signal that has a higher resolution.
2. Description of the Related Art
For conventional use, plasma display devices (PDPs), liquid crystal display devices (LCDs) and electroluminescence display devices (ELs), which can reproduce images at high resolutions, have become popular.
In the process for converting an interlaced video scan signal into a progressive video scan signal, since every other scan signal is an intermittent signal obtained by interlaced scanning performed in the field of an interlaced video scan signal, the intermittent portion should be interpolated by using an interpolated scan signal.
For this interpolated scan signal, a well known, so-called average value interpolation method is used. According to this method, for a static image an inter-field process is performed, and, for example, parallel to the time axis, the average value of pixel signals in adjacent fields along corresponding scan lines is inserted as an interpolated scan signal. For a moving image, an intra-field process is performed, and, for example, the average value of pixel signals along scan lines that are vertically adjacent in the same field is inserted as an interpolated signal.
More specifically, as shown in FIG. 15, when interpolated gray level scan signals y12 to y56 (designated by xe2x97xafs) are to be generated based on real scan signals (designated by ∘s) for individual gray level pixels X1 to X6, first, an upper interpolation element (designated by a xcex94) and a lower interpolation element (designated by a xe2x96xa1) are generated that have gray levels of 1/2 of those of the individual real scan signals. Then, adjacent upper interpolation elements are individually paired with lower interpolation elements and are added together, and interpolated gray level scan signals y12 to y56 are generated and inserted between the real scan signals.
For example, to generate an interpolated scan signal y23 that is to be inserted between real scan signals X2 and X3, a lower interpolation element X2/2, which is designated by a xe2x96xa1 and which is calculated using the real scan signal X3, and an upper interpolation element X3/2, which is designated by a xcex94 and which is calculated using a real scan signal X3, are added together, i.e., the calculation (X2/2)+(X3/2) is performed.
However, when the conventional average value interpolated method is used, it is difficult to reproduce a peak value that is lost during a process performed to convert a sampled video signal into a digital signal, so that image sharpness is deteriorated and a degraded image quality is obtained.
To resolve the above shortcoming, it is an objective of the invention to provide a progressive scan conversion apparatus for a video signal that can reproduce the peak value of a video signal that is lost during digital sampling, and that can effectively obtain a preferable converted image.
It is also an objective of the invention to provide a video signal conversion device that can reproduce the peak value of a video signal that is lost during digital sampling, and that can effectively provide a preferable converted image.
To achieve the above objects, according to an aspect of the invention, there is provided a line interpolation apparatus for converting a video signal for interlaced scanning into a video signal for progressive scanning, which comprises:
lower interpolated element generation means for employing an upper real scan signal, along a real scan line that is above and adjacent to an interpolated scan line, and real scan signals, along a plurality of sequential real scan lines that are vertical relative to the upper real scan line, to generate a lower interpolation element for the upper real scan signal;
upper interpolation element generation means for employing a lower real scan signal, along a lower real scan line that is below and adjacent to the interpolated scan line, and real scan signals, along a plurality of sequential real scan lines that are vertical to the lower real scan line, to generate an upper interpolation element for the lower real scan signal;
inclination detection means for detecting inclination information for an image based on two or more real scan signals, including the upper and the lower real scan signals;
limitation means for adjusting the levels of the upper interpolation element and the lower interpolation element in accordance with the inclination information detected by the inclination detection means, and for generating a first interpolation element and a second interpolation element whose levels are adjusted; and
addition means for adding the first and the second interpolation elements to generate an interpolated scan signal that is to be inserted into the interpolated scan lines that are adjacent to the upper and the lower real scan lines.
In the thus arranged line interpolated apparatus, the lower interpolation element means employs the upper real scan signal (a real scan signal along a real scan line above and adjacent to the interpolated scan line) and real scan signals that are located along a plurality of sequential real scan lines, which are vertical relative to the upper real scan line, to generate the lower interpolation element of the upper real scan signal. And the upper interpolation element means employs the lower real scan signal (a real scan signal along a real scan line below and adjacent to the interpolated scan line) and real scan signals that are located along a plurality of sequential real scan lines, which are vertical relative to the upper real scan line, to generate the upper interpolation element of the lower real scan signal.
The inclination detection means detects inclination information for an image based on two or more real scan signals, including the upper real scan signal and the lower real scan signal. Then, in accordance with the inclination information (the detected information), the limitation means adjusts the levels of the lower and upper interpolation elements to generate the first and the second interpolation elements.
The addition means adds together the first and the second interpolation elements to generate an interpolated scan signal, which it inserts into the interpolated scan line.
According to another aspect of the invention, there is provided a video signal conversion device, which comprises:
first interpolation element generation means for employing pixel data for a first pixel, which is vertically (or horizontally) adjacent to one side of an interpolation pixel, and pixel data for a plurality of pixels, which are vertically (or horizontally) contiguous with the first pixel, to generate an interpolation element for the first pixel positioned beside the interpolation pixel;
second interpolation element generation means for employing pixel data for a second pixel, which is vertically (or horizontally) adjacent to the other side of the interpolation pixel, and pixel data for a plurality of pixels, which are vertically (or horizontally) contiguous with the second pixel, to generate an interpolation element for the second pixel positioned beside the interpolation pixel;
addition means for adding together the first interpolation element and the second interpolation element to generate interpolation pixel data for the interpolation pixel; and
compensation means for generating a compensation value based on the pixel data for the first or Lhe second pixel and the pixel data for the plurality of pixels that are vertically (or horizontally) contiguous with the relevant pixel, and for mixing the compensation value with the pixel data for the first or the second pixel.
With this arrangement, the first interpolation element generation means employs pixel data for the first pixel, which is positioned adjacent to one side of the interpolation pixel, and pixel data for a plurality of pixels that are vertically (or horizontally) contiguous with the first pixel to generate an interpolation element for the first pixel adjacent to the interpolation pixel. The second interpolation element generation means employs pixel data for the second pixel, which is positioned adjacent to the other side of the interpolation pixel, and pixel data for a plurality of pixels that are vertically (or horizontally) contiguous with the second pixel to generate an interpolation element for the second pixel adjacent to the interpolation pixel.
The addition means adds the interpolation elements for the first and the second pixels that are positioned adjacent to the sides of the interpolation pixel, and generates interpolation pixel data for the interpolation pixel.
The compensation means generates a compensation value using the pixel data for the first or the second pixel and the pixel data for the plurality of pixels that are vertically (or horizontally) contiguous with the relevant pixel. Then, to generate pixel data for the first or second pixel, the compensation means mixes the compensation value with the pixel data for the relevant pixel.